Heat oil in a large non-stick frying pan over medium-high heat. Cook onion for 1-2 minutes until slightly softened. Add mince and ground coriander. Season and cook, breaking up mince with a wooden spoon, for 4-5 minutes or until browned. Set aside.
In a large bowl combine lettuce, carrot, cucumber and tomatoes. Drizzle with dressing, season and toss to coat. Top salad with lamb mixture.
Serve with coriander sprigs, chilli, prawn crackers, lime wedges and extra dressing.
Lamb leg steaks, thinly sliced, or lamb meatballs would also work well.
Roll salad up into softened rice paper wrappers for Vietnamese rolls.
Leftover mince mixture can be used in a crunchy baguette, tacos or a noodle bowl.
Vietnamese dressing is available in the Asian section of most supermarkets or Asian grocers.